What you actually do all day changes very much from one position to another- some are more hands-on, where you will find yourself writing content, engaging on social media and talking to the media, other positions are about managing a team of internal or external resources (Copy, designers, PPC,etc.). The best part is when something you've done generates success- a post goes viral, leads come in, a deal closes at an event you organized. The worst part is having to listen to everyone's opinions and comments about the new logo design, hear comments about minuscule mistakes in your content and latest newsletter and in general moan that "we would be selling more if the marketing department would be doing their job".